1. Field of the Invention
The present invention relates to a touch panel device for navigation to be installed in a vehicle such as an automobile, and more particularly to a touch panel device for visually representing, when actuated by an operator's touch, a map, a current position of an automobile, a running locus thereof and so forth on a display unit for example a cathode-ray tube, thereby enabling a driver to acquire necessary information for navigation.
2. Description of the Prior Art
A navigation device installed in a vehicle such as an automobile is generally so contrived that map information inclusive of a whole country map and a plurality of divided district maps are stored in a map memory means any desired map information is read out therefrom in compliance with the requirement of an operator and then is visually represented on a display unit such as a cathode-ray tube constituting a touch panel device, whereby the necessary map for navigation is obtained to meet the requirement.
In such touch panel device, a television picture can be visually represented on a screen of a display unit, and function keys are arrayed on a front panel of the display unit for selecting a desired function relative to television or navigation. In addition to the known function keys, most of the recent devices are equipped with touch switches which are composed of a pattern of actuation keys displayed on the screen. Regarding the touch switches of such type, it is generally customary that a plurality of areas are formed on the display screen, and when any area is touched by an operator's finger, infrared rays are intercepted to output a driving signal. In the switch pattern for actuation is provided in an inner periphery of the screen.
However, since the switch pattern employed in the touch panel device of such type is visually represented in a predetermined area on the display screen at the time of displaying a desired map or television picture required for navigation, a disadvantage exists that the map or television picture being displayed for navigation is concealed by the switch pattern. Therefore, the view field of the screen is narrowed to consequently raise some problems including deterioration of the visual perceptibility and failure in acquiring necessary information.